Percussion and rotary drilling machine

ABSTRACT

A drilling machine has a tool holder shaft on which are mounted a spring and a blocking sleeve which abuts one or the other of two eccentric abutment faces of a manually turnable member. In a first position of the manually turnable member, the spring permits movement of the shaft due to pressure against the workpiece to a first axial position in which the shaft is axially reciprocated by suitable displacement means during rotation, and performs a percussion drilling operation. In a second position of the manually turnable member, the blocking sleeve engages the shaft directly, and blocks the same in a second axial position in which the shaft is not reciprocated but only rotated during drilling, irrespective of the pressure applied by the shaft to the workpiece.

United States Patent [151 3,6 Stroezel [4 1 Sept. 26, 1972 [s41PERCUSSION AND ROTARY DRILLING Primary Examiner-Emest a. Purser MACHINEReinhold Stroeeel, Reuteweg 15,, 7022 Leinfelden, Germany Filed: Nov. 6,I970 Appl. No.: 87,459

Inventor:

[30] Foreign Application Priority Data Nov. 15, [969 Germany ..P i9 57505.4

US. Cl. ..173/l3, 74/22, l73/48 Int. Cl ..E2lc 3/32 Field of Searchl73/l3, 47, 48; 74/22 References Cited UNITED STATES PATENTS 3,433,0823/ i969 Bitter et al ..74l22 3,395,765 8/l 968 Schnettler [73/13 FOREIGNPATENTS OR APPLICATIONS 9/ l 967 Switzerland [73/13 Attorney-Michael S.Striker [57] ABSTRACT directly, and blocks the same in a second axialposition in which the shaft is not reciprocated but only rotated duringdrilling, irrespective of the pressure applied by the shaft to theworkpiece.

ll Clalms, 3 Drawing Figures PATENTED 1973 3.693. 728

a; lrrom/fy 1 PERCUSSION AND ROTARY DRILLING MACHINE BACKGROUND OF THEINVENTION The present invention is concerned with a portable percussiondrilling machine which has a manually operated means for shifting themachine either to percussion drilling, or to rotary drilling.

In accordance with the prior art, the shaft is biassed by a spring inaxial direction, the spring abutting a manually operated sleeve whichhas a cam track by which it is moved relative to the housing so that thedisplacement means for axially reciprocating the shaft can be renderedoperative or inoperative by turning of the sleeve.

Drilling machines of this type according to the prior art have thedisadvantage that the structural parts are complex and expensive tomanufacture due to the required geometrical shape. Furthermore, themanually operated control means are sometimes displaced by the vibrationproduced by the percussion drilling operation. Also, the shifting of themachine between percussion drilling and rotary drilling takes acomparatively long time.

SUMMARY OF THE INVENTION It is one object of the invention to overcomethe disadvantages of percussion drilling machines according to the priorart, and to provide a drilling machine which is shiftable by very simplemeans between percussion drilling and rotary drilling.

Another object of the invention is to provide manual control means,which remain in the position to which they were set even when themachine is subjected to strong vibrations during percussion drillingoperations.

With these objects in view, a manual control means is rotatably mountedin the housing of the machine, and has an abutment face eccentric to itsaxis. In the position rotary drilling," the abutment face supports thetool holder spindler against movement in axial direction so that thetool holder shaft cannot assume the percussion drilling position." Aparticularly safe arresting and blocking of the selected operationalposition, can be obtained by providing on the manual control means, twosubstantially planar faces which are angularly staggered at least 90,and which have different distances from the axis. Preferably, the manualcontrol means has a first abutment face in which the tool holder shaftcan be placed in the percussion drilling position by pressure againstthe workpiece, while the second abutment face effects blocking of thetool holder shaft in a position in which it cannot be moved by pressureto the axial position in which it is axially reciprocated.

One embodiment of the invention comprises a housing; a tool holder shaftmounted on the housing for rotation about an axis, and for axialmovement; first and second displacement means fixedly secured to theshaft and to the housing, respectively, and having an engaged positionin which interacting projections and recesses reciprocate the shaft inaxial direction during rotation for percussion drilling, and an axiallyspaced position in which the shaft only rotates for rotary drilling;actuating means including a blocking means movable along the shaft, anda spring; and manually operated means mounted on the housing for angularmovement about the second axis and having abutment means eccentric tothe second axis.

The actuating means abut the abutment means, which preferably includestwo abutment faces of different eccentricity so that in a first positionof the manually operable means the shah is held by the spring in thefirst axial position in which the first displacement means is spacedfrom the second displacement means until the shaft is pressed against aworkpiece, and the spring yields, whereby the first and seconddisplacement means engage each other and the shaft is axiallyreciprocated.

In a second position of the manually operated means and abutment means,the blocking means directly engages the shaft and blocks the same andthe first displacement means in a second axial direction in which thefirst and second displacement means remain spaced when pressed againstthe workpiece so that the shaft performs a rotary drilling operation.

The spring has ends abutting the shaft and the blocking means,respectively, and the blocking means abuts one or the other abutmentface. The blocking means includes a bearing sleeve having one endabutting the abutment faces, and a thrust ball bearing mounted on theshaft for axial movement and abutting the other end of the bearingsleeve. The spring abuts the thrust ball bearing in axial direction.

A third abutment face may be provided which is engaged by the blockingmeans in a third position of the manually operated means, and is spacedfrom the axis of the manually operated means a distance intermediate thedistances which the first and second spaces are spaced from the same.When the blocking means engages the third abutment face, the shaft isblocked against movement due to the pressure against a workpiece in anintermediate position in which the first and second displacement meansare partly engaged so that the shaft is reciprocated in shorterpercussion strokes than in the first position of the manually operatedmeans. Evidently, a fourth and a fifth abutment face can be provided forselectively blocking the reciprocating shaft in different positionscorresponding to strokes of different length during percussion drilling.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a fragmentary side elevation,partially in longitudinal section;

FIG. 2 is a fragmentary cross-sectional view, illustrating a detail andbeing taken on line "-11 in FIG. I; and

FIG. 3 is a fragmentary cross-sectional view taken on line Il-II in FIG.I and illustrating a modification.

DESCRIPTION OF THE PREFERRED EMBODIMENT The portable percussion drillingmachine 1 has a handle 2 secured to a motor housing 3, and a machinehousing 4. The motor, not illustrated, drives a motor shaft 5 with apinion 6 which is mounted in a bearing 7 carried by a partitioning wall8, by which the motor housing 3 is separated from the machine housing 4.

Motor pinion 6 drives through other gears, not shown, a pair of gears 9and 9a which are rotatably mounted on a shaft 9c to which they can beselectively coupled by coupling pins 9b, each of which has an operativeposition projecting into inner teeth of the respective gear, as shownfor gear 9, and an inoperative position, shown for gear 9a. In thismanner, shaft 90 can be operated at two different speeds, so that gear9d which is fixed on shaft 9c, can drive a gear 10 at different speedsfor rotating the tool holder shaft 11 at different speeds. The manner inwhich the coupling means 9d are operated, is not an object of thepresent invention.

The front end of the tool holder shaft 11 has a threaded portion 12 onwhich a chuck, not illustrated, can be mounted for supporting a drill.Behind the threaded portion 12, the tool holder shaft 11 has a shaftportion 13 of greater diameter, having two flat faces which can beengaged by a wrench during opening and closing of the chuck, and forholding the shafts against rotation during screwing on and taking offthe chuck. The machine housing 4 has an opening 15 at its front end intowhich a bearing block 16 is pressed. Tool holder shaft 11 is mounted ina bearing bore 16' of bearing block 16 by the cylindrical journalportion 13 in such a manner that shaft 11 can rotate and also move inaxial direction. A sealing means 18 in the recess 17 of the bearingblock 16 prevents the loss of lubricating oil along the tool holdershaft 11. Shaft 11 has a flange 19 which is followed by a threadedportion 20 of small diameter, rearwardly of which the cylindrical shaftportions 21, 22 and 23 of gradually reduced diameter are provided.

Gear 10 is screwed onto the threaded portion 20 of shaft 11, and abutsthe flange 19. On its rear face, gear 10 has a ring of alternatingprojections and recesses 24, and a corresponding ring of recesses andprojections 25 is provided on the front face of a disc or ring 26 whichis fixedly secured to housing 4, by screws, not shown.

The threaded portion 20 of the tool holder shaft 11 is separated by ashoulder 20' from the cylindrical shaft portion 21. A coil spring 27surrounds the cylindrical portion 21 and abuts at one end on shoulder20'. The cylindrical portion 21 is separated from shaft portion 22 bythe shoulder 21'. A thrust bearing 28 is mounted on shaft portion 22,slidable on the same in axial direction. The cylindrical end portions 23of shaft 11 projects rearward toward partition wall 8. A projectingportion 29 of partition wall 8 has a bore 30 registering with shaft 11,in which a substantially cylindrical sleeve 31 is mounted forlongitudinal movement in axial direction. The sleeve 31 has an innerbore 32 which has at its rear end for two-fifth of its length a greaterdiameter for receiving a bearing bushing 33. The shaft end portion 23 ofshaft 11 is rotatable and slidable relative to the bearing bushing 33.Spring 27 abutting shaft 11 and gear 10 at one end, presses at the otherend against the thrust bearing 28 urging the same against the front endof the sleeve 31 so that the rear end of the same abuts an abutment face40 of a manually operated control member 37.

At a right angle to the axis of shaft 11, a bore 34 is provided in theprojecting portion 29 of partition wall 8 in which the manually operatedmeans 35 is mounted for turning movement about an axis transverse to theaxis of shaft 11. The manually turnable means 35 has an upper portion 36of small diameter which projects out of bore 34 and carries a knob 37consisting of a synthetic material. Below the knob 37, an annular grooveis provided in the shaft portion 35 in which a sealing ring 39 islocated.

The manually turnable means 35 has at the height of sleeve 31 abutmentmeans in the fonn of two abutment faces 40 and 41, see also FIG. 2,which in the direction of the axis of the manually turnable means 35,are somewhat wider than the sleeve 31, and define an angle of with eachother. The abutment face 40 is closer to the axis of the manuallyturnable means 35, while the abutment face 41 deviates from the circularshape a distance which is substantially a quarter of the radius.

In the inoperative position of the drilling machine, the sleeve 31 abutsabutment face 40, ball bearing 28 abuts sleeve 31 due to the action ofspring 27 and shaft 11 is in a position in which the projections andrecesses of the displacement means 24, 25 are spaced from each other.When the drive shaft rotates pinion 10, transmission shaft 9c is rotatedthrough gears 9 or 9a, and gear 10 is driven by gear 9d together withtool holder shaft 11 so that the same idly rotates.

When the tool at the front end of tool holder shaft 11 is pressedagainst the workpiece, the axial pressure compresses spring 27, sincethe sleeve 31 abuts the abutment means 40. Shaft 11 is placed in aposition in which the projections and recesses of the displacement means24, 25 fully engage each other. Since disc 26 is fixed to the housing,the interacting projections and recesses of the displacement means 24,25 cause axial reciprocation of shaft 12 so that a percussion drillingoperation is carried out. Due to the pressure exerted by the operator onthe handle 2, every time one of the projection of displacement means 24moves over a projection of displacement means 25, the shaft 11 performsa rapid forward stroke, transmitted by flange 19 to shaft 1 1.

When the manually operated means 35 is turned 90 to a position in whichthe abutment face 41 is located opposite the end of the sleeve 31, themanually turnable means pushes the sleeve 31 and thrust bearing 28forward until the thrust bearing 28 engages directly the shoulder 21' ofshaft 11 and displaces the same forwardly to a position in which theprojections and recesses of the displacement means 24 and 25 are axiallyspaced from each other. While the edge formed by the abutment faces 40and 41 engages the sleeve 31, shaft 11 is displaced beyond its normalforward position to a position in which the front edge of flange 19almost engages the inner surface 16" of the bearing block 16. When themanually operated member 35 has been further turned, shaft 11 movesrearward due to the manual pressure until sleeve 31 abuts the secondabutment face 41. in this position of shaft 11 and gear 10 with theprojections and recesses 25, the latter are still axially spaced fromthe projections and recesses 26. Consequently, during continued rotationof the tool holder shaft 11, the same is not axially reciprocated andforms a rotary drilling operation. The distance between the front edgeof flange l9, and the inner face 16" of bearing block 16, is reduced toa small distance to a degree corresponding to the displacement caused bythe edge between abutment faces 40 and 41 to a distance required forrotary drilling.

Due to the additional forward and rearward displacement caused by theedge between the planar abutment faces 40 and 41, together with theaction of spring 27, the result is obtained that the shaft 11 isreliably arrested in the rotary drilling position as well as in thepercussion drilling position, and cannot be shifted to the othercondition by vibrations.

in the position shown in FIG. 1, spring 27 is alternately compressed andexpanded while urging the blocking means 28, 31 into engagement withabutment face 40. [n the position in which the other abutment face 4] isoperative, blocking means 31 and 28 is displaced forwardly to a positionin which the forward race of bearing 28 abuts the shoulder 21' which isdue to the fact that the abutment face 41 is spaced a greater radialdistance than abutment face 40 from the axis of bore 34 about which themanually operated means 35 turns. [n this manner, shaft 11 throughshoulder 21' is blocked by the blocking means 28, 31 in a position inwhich no manual pressure can move shaft 11 with the displacement means24 to a position engaging the displacement means 25.

When abutment faces 40', 40", shown in FIG. 3, which are spaced from theaxis of the manually operated member 35, distances intermediate thedistances which the abutment faces 40 and 41 are spaced, are provided,the shaft 11 is blocked in the manner described above, in anintermediate position in which the projections and recesses ofdisplacement means 24, 25 only partly engage each other, whereby thelength of the percussion strokes is reduced in accordance with theangular position of the manually turnable member 35 which can beeffected by manual operation of knob 37.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofpercussion and rotary drilling machine differing from the typesdescribed above.

While the invention has been illustrated and described as embodied in adrilling machine which can be selectively set to percussion drilling androtary drilling by turning of a manual control means having eccentricabutment faces, it is not intended to be limited to the details shownsince various modifications and structural changes may be made withoutdeparting in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can be applying current knowledgereadily adapt it for various applications without omitting features thatfrom the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations, should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters patent isset forth in the appended claims.

[claim 1. Percussion and drilling machine comprising a housing; a toolholder shaft mounted in said housing for rotation about a first axis,and for limited axial movement; first and second displacement ringssecured to said housing and said shaft, respectively, and havingconfronting faces, each face having alternate projecting and recessedportions, said first and second faces having an engaged position inwhich said shaft reciprocates in axial direction for percussiondrilling, and an axially spaced position in which said shaft onlyrotates for rotary drilling; spring means engaging said shaft for urgingsaid shaft and first displacement ring away from said seconddisplacement ring to said axially spaced position; blocking sleeve meansmounted on the rear end of said shaft for axial movement; and manuallyoperated means mounted on said housing for angular movement about asecond axis perpendicular to, and intersecting said first axis rearwardof said rear end, said manually operated means having at least first andsecond abutment faces spaced different radial distances from said secondaxis and cooperating with said blocking sleeve means so that when saidfirst abutment face cooperates with said blocking sleeve means in afirst angular position of said manually operated means, and the frontend of said shaft is pressed against a workpiece, said spring meansyields and said first displacement ring is pressed against said seconddisplacement ring and said faces engage each other, whereby said shaftis axially reciprocated, and so that in said second angular position ofsaid manually operated means said second abutment face blocks saidblocking sleeve means whereby, when said front end of said shaft ispressed against the workpiece, said shaft is blocked by said blockingsleeve means and said second abutment face in an axial position in whichsaid displacement rings remain in said axially spaced position so thatsaid shaft performs a rotary drilling operation.

2. Drilling machine as claimed in claim 1, wherein said manuallyoperated means include a third abutment face angularly spaced from saidfirst and second abutment faces, and cooperating with said blockingsleeve means in a third angular position of said manually operatedmeans; wherein said third abutment face is spaced from said second axisa radial distance greater than said first abutment face and smaller thansaid second abutment face so that in said third angular position of saidmanually operated means, when said front end of said shaft is pressedagainst said workpiece, said shaft is blocked by said blocking sleevemeans and said third abutment face in an intermediate position in whichsaid projecting and recessed portions of said faces of said displacementrings partly engage each other so that said shaft is reciprocated in ashorter percussion stroke than in said first angular position of saidmanually operated means.

3. Percussion and rotary drilling machine comprising a housing; a toolholder shaft mounted in said housing for rotation about first axis, andfor axial movement; first and second displacement means fixedly securedto said shaft and said housing, respectively, and having an engagedposition in which said shaft reciprocates during rotation for percussiondrilling, and an axially spaced position in which said shaft onlyrotates for rotary drilling; actuating means including a blocking meansmovable along said shaft, and a spring having ends abutting said shaftand said blocking means, respectively; and manually operated meansmounted on said housing for angular movement about a second axis andhaving abutment means eccentric to said second axis, said blocking meansabutting said abutment means so that in a first position of saidmanually operated means, said shaft is held by said spring in a firstaxial position in which said first displacement means is spaced fromsaid second displacement means until said shaft is pressed against aworkpiece and said spring yields whereby said first and seconddisplacement means engage each other and said shaft is axiallyreciprocated, and so that in a second position of said manually operatedmeans and abutment means, said blocking means engages said shaft andblocks said shaft and said first displacement means in a second axialposition in which said first and second displacement means remain spacedwhen pressed against a workpiece so that said shaft performs a rotarydrilling operation.

4. Drilling machine as claimed in claim 1 wherein said abutment meansincludes two abutment faces angularly spaced at least 90 about saidsecond axis and having different distances from said second axis.

5. Drilling machine as claimed in claim 4 wherein said second axisintersects said axis of said shaft; wherein said blocking means abutsone of said abutment faces in said first position of said manuallyoperated means due to the action of said spring; and wherein said shafthas an abutment engaged by said blocking means when the same engages theother abutment face.

6. Drilling machine as claimed in claim 4 wherein said blocking meansincludes a bearing sleeve having one end abutting said abutment means,and a thrust ball bearing mounted on said shaft for axial movement andabutting the other end of said bearing sleeve, and wherein said springabuts said thrust ball bearing.

7. Drilling machine as claimed in claim 6 wherein said shaft has a smallshaft portion surrounded by said thrust ball bearing, and an adjacentlarger portion surrounded by said spring and forming an annular shoulderwith said small shaft portion against which said ball bearing abuts insaid second position of said 8 manually operated means.

8. Drilling machine as claimed in claim 3 wherein said abutment meansinclude a first abutment face engaged by said blocking means by theaction of said spring in said first position of said manually operatedmeans, and a second abutment face spaced a greater distance from saidsecond axis than said first abutment face and engaged by said blockingmeans in said second position of said manually operated means.

9. Drilling machine as claimed in claim 8 wherein said abutment meansincludes a third abutment face engaged by said blocking means in a thirdposition of said manually operated means and being spaced from saidsecond axis a distance intermediate the distances which said first andsecond faces are spaced from said second axis so that said blockingmeans blocks movement of said shaft due to pressure against a workpiecein an intermediate position in which said first and second displacementmeans are partly engaged so that said shaft is reciprocated in shorterpercussion strokes than in said first position of said manually operatedmeans.

10. Drilling machine as claimed in claim 9 wherein said first and seconddisplacement means are first and second discs respectively secured tosaid shaft and said housing and having confronting faces, each of whichhas alternati pg'axially pr jectjng and accessed portions so that In a uy engage position, sai pro ecting portions said first disc completelyenter the recessed portions of said second disc due to said spring,while in the partly engaged position, said projecting portions onlypartly enter said recesses due to said blocking means abutting saidthird abutment face and said shaft.

11. Drilling machine as claimed in claim 10 wherein said first disc isfixedly secured to said shaft and forms a shoulder with the same; andwherein said spring abuts said shoulder.

1. Percussion and drilling machine comprising a housing; a tool holdershaft mounted in said housing for rotation about a first axis, and forlimited axial movement; first and second displacement rings secured tosaid housing and said shaft, respectively, and having confronting faces,each face having alternate projecting and recessed portions, said firstand second faces having an engaged position in which said shaftreciprocates in axial direction for percussion drilling, and an axiallyspaced position in which said shaft only rotates for rotary drilling;spring means engaging said shaft for urging said shaft and firstdisplacement ring away from said second displacement ring to saidaxially spaced position; blocking sleeve means mounted on the rear endof said shaft for axial movement; and manually operated means mounted onsaid housing for angular movement about a second axis perpendicular to,and intersecting said first axis rearward of said rear end, saidmanually operated means having at least first and second abutment facesspaced different radial distances from said second axis and cooperatingwith said blocking sleeve means so that when said first abutment facecooperates with said blocking sleeve means in a first angular positionof said manually operated means, and the front end of said shaft ispressed against a workpiece, said spring means yields and said firstdisplacement ring is pressed against said second displacement ring andsaid faces engage each other, whereby said shaft is axiallyreciprocated, and so that in said second angular position of saidmanually operated means said second abutment face blocks said blockingsleeve means whereby, when said front end of said shaft is pressedagainst the workpiece, said shaft is blocked by said blocking sleevemeans and said second abutment face in an axial position in which saiddisplacement rings remain in said axially spaced position so that saidshaft performs a rotary drilling operation.
 2. Drilling machine asclaimed in claim 1, wherein said manually operated means include a thirdabutment face angularly spaced from said first and second abutmentfaces, and cooperating with said blocking sleeve means in a thirdangular position of said manually operated means; wherein said thirdabutment face is spaced from said second axis a radial distance greaterthan said first abutment face and smaller than said second abutment faceso that in said third angular position of said manually operated means,when said front end of said shaft is pressed against said workpiece,said shaft is blocked by said blocking sleeve means and said thirdabutment face in an intermediate position in which said projecting andrecessed portions of said faces of said displacement rings partly engageeach other so that said shaft is reciprocated in a shorter percussionstroke than in said first angular position of said manually operatedmeans.
 3. Percussion and rotary drilling machine comprising a housing; atool holder shaft mounted in said housing for rotation about first axis,and for axial movement; first and second displacement means fixedlysecured to said shaft and said housing, respectively, and having anengaged position in which said shaft reciprocates during rotation forpercussion drilling, and an axially spaced position in which said shaftonly rotates for rotary drilling; actuating means including a blockingmeans movable along said shaft, and a spring having ends abutting saidshaft and said blocking means, respectively; and manually operated meansmounted on said housing for angular movement about a second axis andhaving abutment means eccentric to said second axis, said blocking meansabutting said abutment means so that in a first position of saidmanually operated means, said shaft is held by said spring in a firstaxial position in which said first displacement means is spaced fromsaid second displacement means until said shaft is pressed against aworkpiece and said spring yields whereby said first and seconddisplacement means engage each other and said shaft is axiallyreciprocated, and so that in a second position of said manually operatedmeans and abutment means, said blocking means engages said shaft andblocks said shaft and said first displacement means in a second axialposition in which said first and second displacement means remain spacedwhen pressed against a workpiece so that said shaft performs a rotarydrilling operation.
 4. Drilling machine as claimed in claim 1 whereinsaid abutment means includes two abutment faces angularly spaced atleast 90* about said second axis and having different distances fromsaid second axis.
 5. Drilling machine as claimed in claim 4 wherein saidsecond axis intersects said axis of said shaft; wherein said blockingmeans abuts one of said abutment faces in said first position of saidmanually operated means due to the action of said spring; and whereinsaid shaft has an abutment engaged by said blocking means when the sameengages the other abutment face.
 6. Drilling machine as claimed in claim4 wherein said blocking means includes a bearing sleeve having one endabutting said abutment means, and a thrust ball bearing mounted on saidshaft for axial movement and abutting the other end of said bearingsleeve, and wherein said spring abuts said thrust ball bearing. 7.Drilling machine as claimed in claim 6 wherein said shaft has a smallshaft portion surrounded by said thrust ball bearing, and an adjacentlarger portion surrounded by said spring and forming an annular shoulderwith said small shaft portion against which said ball bearing abuts insaid second position of said manually operated means.
 8. Drillingmachine as claimed in claim 3 wherein said abutment means include afirst abutment face engaged by said blocking means by the action of saidspring in said first position of said manually operated means, and asecond abutment face spaced a greater distance from said second axisthan said first abutment face and engaged by said blocking means in saidsecond position of said manually operated means.
 9. Drilling machine asclaimed in claim 8 wherein said abutment means includes a third abutmentface engaged by said blocking means in a third position of said manuallyoperated means and being spaced from said secoNd axis a distanceintermediate the distances which said first and second faces are spacedfrom said second axis so that said blocking means blocks movement ofsaid shaft due to pressure against a workpiece in an intermediateposition in which said first and second displacement means are partlyengaged so that said shaft is reciprocated in shorter percussion strokesthan in said first position of said manually operated means. 10.Drilling machine as claimed in claim 9 wherein said first and seconddisplacement means are first and second discs respectively secured tosaid shaft and said housing and having confronting faces, each of whichhas alternating axially projecting and recessed portions so that in afully engaged position, said projecting portions said first disccompletely enter the recessed portions of said second disc due to saidspring, while in the partly engaged position, said projecting portionsonly partly enter said recesses due to said blocking means abutting saidthird abutment face and said shaft.
 11. Drilling machine as claimed inclaim 10 wherein said first disc is fixedly secured to said shaft andforms a shoulder with the same; and wherein said spring abuts saidshoulder.